Drill grinding machine



Oct. 18, 1938.

A. A. BAHUAUD DRILL GRINDING MACHINE Filed Jan. 25, 1937 2 Sheets-Sheet 1 AdflQrfKJSUSl'g @uhuaQd 1 I N VENT K QM A r A. A. BAHUAUD DRILL GRINDING MACHINE '2 Sheets-Sheet 2 Filed Jan. 25

Adrien Avs sn e Bahuaud I N vaNToK 1 flu ATTV Patented Oct. 18, 1938 UNITED STATES PATENT OFFICE Application January 25, 1937, Serial No. 122,138 In France February 5, 1936 5 Claims.

It has been found that a high efliciency together with a great accuracy of the dimensions of the pierced holes may be obtained with a two- 4 groove drill in which the portions of .the two relieving surfaces lying adjacent the cutting edges and determining the same are formed by helicoidal or substantially helicoidal surfaces the axes of which are parallel and eccentric with reference to the longitudinal axis of the drill. Said helicoidal surfaces may be extended rearwardly by conical or other surfaces which do not engage the bottom of the hole that is drilled.

The present invention has for its'object to provide a machine for grinding. drills so as to obtain such helicoidal relieving surfaces.

The invention will now be fully described with reference to the accompanying drawings, in

which:

Fig. 1 shows the end of a drill in the position for grinding. 1

Fig. 2 is an elevational view of the grinding machine.

Fig. 3 is a plan view of this machine.

Fig. 4 is an end view of the aggregate of sleeves of the said machine.

Fig. 1 shows a drill I as may be obtained with the machine according to the invention. Each relieving surface'of said drill I consists, firstly, of a helicoidal or substantially helicoidal surface A or A whose axis, passing through 27 or b, is eccentric with reference to the longitudinal axis of the drill, but is parallel with this axis, the eccentricities of the two axes passing through I; and b respectively, being equal; and secondly, of a conical surface B or B which is joined to the helicoidal surface A or A on the line b'd or lid.

The cutting edge of the drill consists of the line abcba'. From a to b, this edge is formed by the intersection of the helicoidal surface A and the discharge groove C, from b to b it is formed by the intersection of two helicoidal surfaces A and A, and from b to a, by the intersection of the helicoidal surface A and the second discharge groove C.

Figs. 2, 3 and 4 show by way of example a machine for grinding the above-mentioned drill.

The said machine comprises a disc-shaped grinding wheel 2 which is keyed to a shaft 3 by which it is rotated, for instance in the direction of the arrow j (Fig. 2). The said shaft is mounted in bearings 4 located on the machine frame 5, and can be driven by any suitable transmission gear. r The said grinding wheel operates by its edge 5 (Fig. 3) which is determined by the intersection of its cylindrical surface with one of its faces. It should have a sufficientdiameter in order that one may consider as rectilinear, the portion mn (Fig, 2) of the aforesaid edge which is in contact with the drill I to be sharpened.

The drill I is held against the said wheel by a chuck I with concentric jaws, which is clamped by means of a milled nut 8 or otherwise. The chuck I is centered in a sleeve 9; a milled nut I0, bearing against a shoulder II on the said chuck, serves to hold the said chuck in the sleeve 9 in any angular position, but always in a determined longitudinal position.

A matching device, consisting for example of a pointer 34 mounted on the sleeve 9 (Fig. 4) which may be brought into coincidence with either of two lines 35-36 having diametrically opposite positions on the chuck I (or inversely) is usedafter releasing the chuck-to give this latter two positions with reference to the said sleeve, which are thus diametrically opposite.

The sleeve 9 is mounted in a second sleeve I2. The sleeve 9 together with .the drill I may be given an eccentric position with reference to the said sleeve I2. The connection between the sleeves 9 and I2 is such that the axis of the sleeve 9 may be given a movement of rectilinear translation at right-angles to the said axis. Fig. 4 shows a form of the connection between the sleeves 9 and I2. This connection is obtained by means of an axle I3. The are described by one of the points on the axis 0 of the drill is practically in coincidence with a straight line which is perpendicular to the radius b-I 3 of the sleeve I2 passing through the axis I3, and the direction of the movement will obviously depend upon the choice of the position of the axis of oscillation I3.

The eccentricity of the axis 0 of the sleeve 9 and of the drill I with reference to the axis of the sleeve I2 is obtained by the used a pushpiece I4 screwed into a handle I5, which latter is screwed at 16 into the sleeve I2 (Figs. 2 and 4), and this eccentricity is adjusted by bringing the suitable point of the drill, b for instance, chosen as the axis of one (such as A) of the two helicoidal surfaces determining the cutting edge bed of the drill, into contact with the pointed part of a I finger H which is mounted on the sleeve I2 and whose end is located exactly upon the axis of the said sleeve I2.

A reaction spring I8 (Fig. 4) mounted between the sleeves 9 and I2 and having a permanent action, holds the sleeve against the push-piece I4.

The sleeve I2 is located within a collar 28 which is coaxial with the sleeve, and with reference B of the drill.

to this collar it can be given a helical or practically helical movement. This movement is obtained by means of the handle [5. The pitch is adjustable at will by the use of an inclined part 2! whose position on the said collar can be regulated by means of a nut 22 and a lock-nut 23 (Fig. 4). A roller 23 (Fig. 2) mounted on the handle I4, and a cooperating roller 25, maintain the contact with the inclined part 2|. A spring 25, mounted between the members l2 and 20, or a like device, urges the sleeve 12 into a stopped position, this being the normal position for which the operative edge 6 of the grinding wheel will coincide with the line of separation b'b or M of the part A or A, and of the rear part B or B of the relieving surfaces, provided the point b or b of the drill shall have been brought upon the end of the guide push-piece l4.

The drill beingsupposed to have been in con tact with the grinding wheel practically in the diametrical plane XX (Fig. 2), the aforesaid device is inclined from this horizontal plane XX by an angle at which is practically the complemerit of the angle between the lips of the drill and the axis YY of the drill. This device can also be adjusted, as to rotation about a vertical axis ZZ in such way that the vertical plane YY-ZZ passing through the axis YY of the drill shall form with the plane perpendicular to the axis of the grinding wheel, i. e., with the plane UU (Fig. 3) of the said wheel, an angle which is equal to the angle a of relief (Figs. 2 and 3) at the periphery of the drill in the helical portion A or A.

An axis of oscillation VV (Fig. 2) which is inclined from the vertical axis 22 permits of obtaining the rear part B or B of the relief. The direction of this axis W is such that the angle 1 formed with the tangent ZZ to the grinding wheel will be equal to the half-angle at the apex which is desired for the conical relieving urfaces B and A spring 21 which is mounted for instance between the pivot axle 28 and its bearing 29 constantly urges the whole device into an angular position, determined in normal position, in which the operative edge 6 of the grinding wheel 2 will coincide with the line of separation 17'!) or bd between the rear part B or B and the front part A or A of the relieving surface of a lip of the said drill. It will be necessary to overcome the resistance of the spring 21 in order to form the surface B or B by operating a handle 30.

Slides 3| and 32 situated at the lower part, whose directions are at right-angles, or like devices, serve to adjust the position of the drill with reference to the grinding wheel, and to take up the rear of this latter. The slide 3| is provided with a vernier 33.

With this construction, a drill is sharpened in the following manner. The slide 3| is slightly released; the sleeve 12 is in the normal position, and the sleeve 9 is slightly released in order to provide for the rotation of the chuck l, but without any appreciable longitudinal clearance. The push-piece is driven in somewhat more than is considered necessary, and the drill is lightly held in the chuck in such way as to project but little from the finger l1.

By acting upon the push-piece l4 and the milled nut In, the drill is brought into the position shown in Fig. 2, and the point b may coincide for example with the end of the finger I! in contact with the helical groove from a to b.

I! by the I in line with the pointer- 34 of the sleeve 9, after which the nut I0 is again screwed down. The

.coidal surface to be ground coincides with one The nuts 8 and H! are then screwed tight. By means of the slides 3I' and 32, the drill is brought into contact with the operative edge 6 of the grinding wheel, which latter is now 10- .i cated at bd'. The slide 3! is now slightly brought forward in order to make the first cut. When theslide has advanced to a sufilcient degree, the device is pivoted on the axis VV by the handle 30, so as to form the rear surface B, then returning to the normal position. The drill is then given the helical movement required for the formation of the front relieving surface A, by a means of the handle, l3, the inclined part 2| having been previously adjusted according to the necessary relief and to the diameter of the drill.

A certain number of cuts are made, as required by the state of the drill. The slide 3| is then sufificiently released, the nut I0 is unscrewed,

and the second line 36 on the chuck is brought drill has now been turned through 180 on its axis, and the work is recommended for the second lip of the drill, in the same manner as for the first, and it is stopped upon arriving at the same divisions of the vernier of the slide 3|.

Obviously, the said invention is not limited to the embodiment herein described and represented, which is given solely by way of example. Having now described my invention what I claim as new and desire to secure by Letters Patent is: 1. A drill grinding machine for grinding the helicoidal relieving surfaces of a two groove drill with two helicoidal relieving surfaces, comprising in combination a rotary grinding wheel, a cylindrical .sleeve adapted to carry the drill to be ground in a position in which the axis of said drill is parallel and eccentered with reference to the axis of said sleeve, a collar adapted to slidably and rotatably embrace said sleeve so that said drill occupies a position in which a generatrix of the helicoidal surface to be ground substantially coincides with one of the outer edges of the rim of said grinding wheel and means adapted to helically displace said sleeve with reference to said collar about the axis of said sleeve and including a helical cam surface on said collar, a cam follower rigidly connected to said sleeve and caused to follow said cam surface, whereby, when said sleeve is moved within said collar, it is obliged to follow a helical path determined by said helical cam surface. I

2. A drill grinding machine for grinding the helicoidal relieving surfaces of a two groove drill' with two helicoidal relieving surfaces, comprising in combination a rotary grinding wheel, a drill holding chuck, afirst sleeve in which fits said chuck, clamping means adapted to fixedly hold said chuck in said first sleeve, a second sleeve surrounding with clearance said first sleeve, connecting means adapted to connect said first and second sleeves so that the axis of said drill is parallel with the axes of said sleeves, adjusting means adapted to adjust the distance between the axes of said drill and of said second sleeve, a collar adapted to slidably and rotatably embrace said second sleeve so that said drill occupies a position in which a generatrix of the heliof the outer edges of the rim of said grinding wheel, and means adapted to helically displace said second sleeve with reference to said collar about the axis of said second sleeve.

2, in which said connecting means comprise an axle parallel with the axes of said second and said first sleeves and secured to said second sleeve in an eccentered position, said first sleeve being adapted to pivot about said axle and said axle being equally distant from the axis of said first sleeve and from the axis of said second sleeve.

4. A drill grinding machine as claimed in claim 2 in which said connecting means comprise an axle parallel with the axes of said second and said first sleeves and secured to said second sleeve in an eccentered position, said first sleeve being adapted to pivot about said axle and said axle being equally distant from the axis of said first sleeve and from the axis of said second sleeve, and in which said adjusting means comprise a pushing member and spring means, said pushing member being adapted to rotate said first sleeve about said axle against the action of said spring means.

'5. A drill grinding machine as claimed in claim 2, further comprising a stop on said second sleeve, a stop surface on said collar, spring means adapted to rotate said second sleeve so as to bring said stop and said stop surface into contact, said stop being so adjusted that when it is in contact with said stop surface, after the eccentricity between said first and second sleeves has been adjusted, the said one edge of said grinding wheel coincides with the rear end gene'ratrix of the helicoidal relieving surface of the drill.

ADRIEN AUGUSTE BAHUAUD. 

